Scale-up of Bioprocesses
517
Acetolactate —» CO
2
+ Acetoin
(acetolactate decarboxylase)
Acetoin + NADH + H+
<->
2,3 butanediol
(butanediol dehydrogenase)
At pH-values higher than 6.5 also acetate is formed.
b) Compare the residence time in the tube to the characteristic times for oxygen consumption and
substrate consumption. Assume that the dissolved oxygen concentration in the reactor is 10% of DOT,
and that the system is to be operated as a chemostat with a glucose concentration of 10 mg L"1
and a
biomass concentration of 4 g L'1.
What are your conclusions?
c) The experiments by Amanullah et al, were in fact made as batch cultivations, with oxygen limited
conditions also in the stirred tank reactor. A control experiment, in which base addition was made in the
reactor instead of the loop was also made. The following yields were found
Residence time in loop
(S)
Yield of acetic acid
(gg1
)
Sum of yields of acetoin
and butanediol
(g fi'1)
Biomass yield (g
g ‘)
(no loop)
0
0.30
0.49
30
0.002
0.31
0.52
60
0.023
0.29
0.51
120
0.076
0.23
0.50
240
0.083
0.22
0.50
120*
0
0.30
0.50
*
pH control made in the stirred tank reactor instead of in the loop.
Discuss the results.
REFERENCES
Amanullah, A„ McFarlane, C. M., Emery, A. N., and Nienow, A. W. (2001). A scale-down model to simulate spatial pH
variations in large-scale bioreactors.
Biotechnol. Bioeng.
73:390-399
Bird, R. B., Stewart, W. E., and Lightfoot, E. N. (2002). Transport phenomena, 2nd ed,, John Wiley&Sons, New York
Bisio, A., and Kabel, R. L, (1985) Scale-up of Chemical Processes - Conversion of Laboratory Scale Tests to Successful
Commercial Size Design. John Wiley
&
Sons, New York
Blanch, H. W., and Clark, D. S. (1997). Biochemical Engineering, Marcel Dekker, New York
Bourne, J. R (1997). Mixing in single-phase chemical reactors, in Mixing in the Process Industries, 2nd edition, Butterworth
Heinemann,
Brune, A. (1998). Termite guts: the world’s smallest bioreactors.
Trends Biotechnol.
16:16-21
Bylund, F., Castan, A„ Mikkola, R., Veide, A., and Larsson, G. (2000) Influence of scale-up on the quality of recombinant
human growth hormone.
Biotechnol. Bioeng.
69:119-128
Chisti, Y„ Moo-Young, M. (2001) Bioreactor design, in:
Basic Biotechnology
(C. Ratledge and B. Kristiansen, eds), Cambridge
University Press, Cambridge
Chilton, T. H., Drew, B., Jebens, R. H. (1944). Heat transfer coefficients in agitated vessels.
Ind. Eng. Chem.
36:510-516
Cooney, C. L. (1983). Bioreactors: Design and operation.
Science
19:728-740
Einsele, A., Ristroph, D. L„ and Humphrey, A. E. (1978) Mixing times and glucose uptake measured with a fluorometer.
Biotechnol. Bioeng.
20:1487-1492
Geankoplis, C. J. (1993). Transport processes and unit operations, 3rd ed„ Prentice Hall, Englewood Cliffs, New Jersey
George, S., Larsson, G., Enfors, S.-O. (1993). A scale-down two-compartment reactor with controlled substrate oscillations.
Metabolic response of
Saccharomyces cerevisiae. Bioproc. Eng.
9:249-257
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